Monero may not be a pump and dump coin, but there is certainly a lot of dumping going on, and the price is starting to suffer.

I think the answer is no. First of all it is questionable whether you would really want to hold wealth long term on a sidechain. The security assumptions (even when it comes to things like network hash rate, but in other more fundamental respects as well) are questionable. It is more plausible you might want to use services or features on a side chain by moving your bitcoins there and then, relatively quickly, moving them back to the more secure main chain. For example, this might be be used for mixing, by moving your coins to a sidechain with ring signatures, transacting and then moving them back.

But this ends up being a lot like using a Bitcoin mixer, with many of the same issues such as simultaneity. For example, imagine you are making a donation to some controversial organization and you want to delink the bitcoins you are donating.

So you go ahead and move your coins to a ring-sig sidechain, move them around a few times, and then move them back. Unless other people are doing this at the same time, when you move your coins back to the main chain, you will get the same coins back that you started with.

Alternately, perhaps the organization wants to be all anonymous and stuff, so it publishes an address on the sidechain, and you donate to them there. They then withdraw the coins back to the main chain, and they get the exact Bitcoins you sent to the side chain.

Obviously if there are a few other people doing the transfers at the same time, there is a degree of mixing, but it is fairly limited.

I don't think a side chain with a specialized purpose can achieve the same degree of anonymity as a coin designed for that purpose, where the entire chain is being mixed and remixed continually. That is an emperical question though. It is possible that a Bitcoin side chain could get more usage and greater trust of its security for long term holdings than Monero will have. More usage would address the mixing issue to a some extent and trust in the security would address the need to constantly move coins back and forth (though there still may be a loss of network effect here). None of this is clear at all.

I also think it is possible the market may simply reject the notion of adopting the Bitcoin currency for everything. It will be an interesting experiment to decouple new features from using a different currency. We may well find that the reason for altcoins is not the features!