so i ask, if there are billions of SC's in action processing tx fees, where will all the badly needed tx fees come to support Bitcoin in the long run when the blockchain rewards are gone?
The BTC block reward will be more than enough to protect the network for another 20-30 years.
If after that time most transaction fees shift to MM'ed sidecoins to the extent that there are not enough fees on the main chain to support the main chain then one of 2 things will happen, either: 1) Adjustments will be made to shift MM fees from sidecoins to the main chain (after all sidecoins need this too since their protection is based on MM'ing with the main chain) or 2) some side chain will become the main chain since essentially the main chain was abandoned. Note: this wouldn't hurt BTC since at most 21M BTC would transfer over the 1:1 peg.
i actually think the underlying problem here is that some of us see Bitcoin as Sound Money who's sanctity is to be protected at all costs, like me, and others see it as an avenue to develop stocks, bonds, community currencies, assurance contracts, smart contracts, etc, etc.
if you don't buy into this view, then SC's seem like a natural thing. who cares if somehow a little inflation, centralization, or trust requiring needs slip in the backdoor?
I only see bitcoin as
Sound Money, it is the entire reason I support the project. If the concept is broken in the slightest I will abandon ship.
Sidechain's do nothing to effect the Sound Money aspect.
Sidechains are sub-coins that only exist within the 21M supply limit and this is enforced with 1:1 pegging. Altcoins (meaning new coins outside of the 21M limit) are the only real threat Bitcoin has, because they are the real threat that can inflate the money supply. 1 year ago I saw altcoin's as becoming a real problem and had second thoughts about the project because "anyone can create a coin".
However the past year has shown that network effects are working as intended, and I'm more comfortable with the altcoin threat not being a problem.
Once you understand that sidechains are just that "sub-coins to Bitcoins 21M controlled supply", then it is natural to see sidechains as part of the original Sound Money plan. They simply offer a mechanism to increase functionality without a hard fork. Period