@p2p exchange -- I didn't mean to conflate p2p and ATM solutions, because I think the ATM solution will be relatively centralized. I don't see any of the really ambitious p2p exchange ideas ever taking off -- those decentralized protocol layer schemes. Maybe I lack vision. Instead, I think p2p will mostly stick to listing sites like LocalBitcoins.
ATMs are going to have a really complicated, capital-sucking time ahead of them long-term, I think, because I think we'll find we can't trust the exchanges in existence to not ruin businesses with slow turnaround time or by "accidentally" blacklisting ATM accounts (as recently happened with Bitstamp and the Vancouver ATM). I think, instead, ATM operators will bite the bullet and form their own exchanges (especially since many are forced to comply with horrible MSB crap already and already require large operating floats) which will have local, regional, or national markets depending on how laws work in a particular area -- I think we'll see "exchange disunification" for a while, where people generally don't use one global exchange to transfer multiple fiat currencies in and out for BTC. Lot of ways it could play out. Someone will definitely want to be arbing, so maybe there will be a quiet venture launched by Robocoin, Lamassu, or an ATM operator federation which makes giant stacks of cash by forming a "backbone" exchange which arbs with all the local, regional, and national ATM exchanges to ensure a relatively stable price across the world whenever there's deviation.
I really don't see tx fees being a big deal because altcoins have basically already solved it with relatively sucky networks, and I think just shoving more, cheaper transactions into blocks is just kicking the can down the road. Devs have never (AFAIK) pushed Bitcoin as a micropayments platform, and if usage continues exploding faster than tech can keep up, it won't go back to being one. It would be very expensive as far as resources for full nodes... kind of like an ultra-progressive tax where we let the wealthy first-worlders generously (or maliciously) control our nodes, and to a lesser extent, this is how Bitcoin is right now -- you need uncapped DSL+ (preferably cable+), you need a modern PC, and you have to want to run it enough to sacrifice hard drive speed, CPU processing time, and bandwidth to it (or pay for VPS/dedicated). In my case, where I rely on a mobile data connection, I'm counted as a full node by the node crawlers, but I'm really not because I started running my node selfishly by explicitly limiting Bitcoin's bandwidth to a point where it's not really contributing anything, only leeching.
In almost all instances, transactions cost significantly more to store and pass around than are paid in fees, so smart fees (unless they significantly increase fees on average) seems low priority and potentially detrimental compared to shrinking the blockchain and decentralized protocol layers which allow the combination of transactions to cut down on overhead. CoinJoin, for example, has major benefits both in reducing blockchain size, improving pseudonymity, and in cutting down tx fees dramatically. It's a major objective improvement to just about every aspect of Bitcoin, so that's what I'm really looking forward to. I think, to maintain Bitcoin's very strong network, there's also a need to figure out how to subsidize node costs (such as by a foundation mailing out copies of the blockchain on USB drives) and somehow figure out a fair payment mechanism for them (maybe just a foundation giving monitored full nodes a kind of salary, or paying universities). I worry about a trend toward capping Internet bandwidth consumption in more Western countries like is already seen by many less-developed nations (and some Western nations). The precedent set with the recent Comcast/Netflix blackmail is worrying, too -- "Bitcoin" won't be able to pay Comcast $400M to "fix" Bitcoin traffic, but it's too soon to tell if Comcast and other ISPs will be empowered to start really cracking down on "low-priority" (non-subsidized) traffic they can't adequately serve due to infrastructure inadequacies and severe over-selling on the ISPs' parts.
I think alt-coins like LTC and FTC (or Quark... whatever the new Feathercoin is) will have a more accepted and well-defined niche... they'll be relatively insecure, and it's where you what you want to keep your short-term spending money in due to the lower fees which come from insecurity (and lack of lite node wallet clients!). Weaker networks are where you want to do micro-payments; TANSTAAFL. With multi-coin wallet clients, I think that transition will be major and fast if major improvements to BTC like CoinJoin aren't widely implemented, but I have no idea when it will happen outside "within the next year." If we do see a major transition like that with BTC in its current state, I think it could make the VCs leave Bitcoin and either run away back to the sidelines or start wider-scope cryptocurrency businesses rather than narrow-scope Bitcoin businesses.