Please do elaborate because you didn't explain at all how sidechains are not remotely scalable...+ various other points
I'm not saying sidechains can't work - I'm saying you can't remotely expect them to displace alt coins because they are *not* altcoins.
Of course, nobody can know how this will all go in the future, but I think one of the things that characterises your view and doesn't mine is your comparison of Bitcoin to TCP/IP.
Such an analogy is a big mistake.
Bitcoin is not at all like the fundamental internet network layers. For a start it isn't an international technological standard, it is a private monetary brand. I wouldn't even liken it to a high level protocol (of which there are many such as http, JSON, SMPT etc).
The market can come up with new decentralised currencies anytime it wants and have them incrementally adopted. What matters isn't whether it's mechanically interfaced with bitcoin but rather that it's economically interfaced with it by way of a market value.
Maybe sidechains will have a future and maybe they won't, but I don't think it will have any bearing on the future for alts. Cryptocurrencies are already extremely fluid and interchangeable - far more so than fiat currencies. That fact alone implies there will be a comfortable co-existence to mutual benefit of bitcoin as a reserve and altcoins as a kind of "transport / liquidity layer".
Only a few months ago the combined shitcoin market cap was ~25% of Bitcoins market cap. Now it's closer to 10%. That would suggest the altcoin cesspool is shrinking and hopefully will be completely phased out.
It would suggest no such thing. Bitcoin lost 80% of its marketcap against fiat last year. Are you concluding from that that Bitcoin has no future, is "shrinking and..will be completely phased out" ?
And why are you calling it the "shitcoin market" ? Do you want to be taken seriously or not ?
Bitcoin has survived as long as it has because that altcoin market exists. Altcoins have demonstrated that blockchain technology is not limited to the monetary and technological properties that bitcoin alone exhibits. It has served as a stepping stone and a liquidity engine for bitcoin trading as well as all kinds of innovative tech evolutions. The reason its marketcap declined is exactly the same as the reason bitcoin's declined - speculative consolidation and profit taking. Technical development, innovation and market involvement however are more active than ever.
I don't know why I'm even defending this point of view because it's so self evident. The idea that alts are not going to have a huge role if the crypto-economy blows up is ludicrous. Of course they will - bitcoin has already been left in the dust by altcoin technology and sidechains are not even on the drawing board.
As I say - BTC will likely have the role of a cryptocurrency monetary reserve, but any alt that has a value measurable in bitcoin which is infinitely more practical in specific markets is not going to disappear.