Lightning network is the only thing that Bitcoin needs right now. Once that is in place, there is no need to implement other altcoins because of them not having any 'advantage' over Bitcoin anymore. The only thing altcoins do better than Bitcoin right now, is offering faster confirmation times, and that for a lower price. I however have to point out that this is mainly the result of lacking altcoin usage. As soon as whatever altcoin sees its usage grow exponentially, like what happened with Ethereum for example, then they will suffer from network cluttering as well, which results in higher fees. I just can't say anything about when lightning network gets activated. I wish as soon as possible, but without it being tested through properly, it won't be launched.
I´d argue that altcoins are also better at enriching their founders.
Most of them will probably linger around for quite a while, but will only
trade for a fraction of their former value when the altcoin bubble finally bursts.
The real question is when this will happen. Many high-profile ICOs that raised
millions of $ will have to deliver results at some point and when they fail to do that
it could disincentivize people from investing in upcoming ICOs. On the other hand
it is possible that the whole scene grows so much that every disgruntled investor
is easily replaced by new people, who are getting into the cryptocurrency scene
due to the prospect of "easy money".
Regarding the Lightning Network:
People are already using it on Mainnet:
https://p2sh.info/dashboard/db/lightning-network?orgId=1
Of course the teams behind the various Lightning implementations currently
advise people to be cautious and only use the Lightning implementations on testnet,
but apparently many people are happy to throw caution to the winds.