This is not correct. If you hand mining over from a decentralized system of tens of thousands of GPU miners to one ASIC manufacturer it does not increase the network security.
For this reason we need to change the hashing algorithm from time-to-time, so that no ASIC can be produced (ASIC production takes a lot of time).
Honestly, it's just not worth it. In a few months, the same amount of time that it would take to find a new algorithm, if not longer, and implement it, Dash will be on Evolution. With Evolution, transactions will be approved by Masternode Quorums and the hash will only be used to randomly group these Masternodes into quorums. The miners will still include transactions into the blockchain, however, they will have no choice as to which transactions to include. They must only include locked transactions that passed a Masternode Quorum first. If they try to include anything else, it will be rejected by the Masternode network and the miner will lose the block.
It simply will become a new and infinitely more secure network soon enough. So please don't fret. Once this is in place, it won't matter if we only have one single miner.
1) The impact on users would be minimal, since transactions would still "go through"
2) The malicious miner would only be foregoing any fees associated with the "skipped" transaction
The reason mining concentration is a big deal in Bitcoin is because of the risk of a double spend. With InstantX mitigating this risk, there isn't really even an incentive for a malicious miner anymore, thus no worries about mining concentration.
As long as SOME of the mining power is running as planned, any impact of an attack would be minimal. At worst, you'd have some delays of a few blocks before people could turn around and spend their outputs. Why would anyone spend millions on mining equipment to do that?
I think people are losing sight of the fact that X11 was only meant to be ASIC resistant for a year or two to help with initial distribution... following a similar path as Bitcoin. I don't think anyone mines Bitcoin at home on their CPUs or GPUs anymore... that doesn't seem to be holding Bitcoin back. I think we got about all we expected out of X11 in terms of getting Dash into the hands of anyone in the mining community that would want to get their hands on some Dash without paying for it. So we got the distribution benefits.
As far as the arguments that ASICs hurt Litecoin... Litecoin's lack of development hurt Litecoin. One data point doesn't make the case that ASICs are bad for price. Bitcoin has ASICs and it seems fine. So I think we have exactly two data points to work with and one goes against the hypothesis that ASICs are bad for price. Pretty weak argument if you ask me.