In 10 years time I think cryptocurrencies will be adopted in every segment of economy and Bitcoin will cost at least 1 Million dollars. The whole world will be digitalized and robots will do a lot of things that we are doing right now.
you are right, bitcoin requires 3 confirmations to ship and takes 15 minutes for 1 confirmation but I think there are still many rivals in terms of transaction speed in the next 10 years.
I don't have much hopes at seeing big improvements in speed and transaction capacity on-chain. Just think about the massive drama that segwit brought. It was years of discussions until it actually happened, not without side effects (bitcoin cash was born and we now have this ridiculous war about who is the real bitcoin and whatnot). Further attempts will only bring more of that. There will no consensus.
Second layer scaling will get better in the future, I have no doubts about that. As far as altcoins go, I seriously doubt an altcoin without the store of value property will challenge bitcoin just because it's fast and cheap. People will rather use second layers on bitcoin once wallets are widespread and easy to use just to not go through the annoyance of dealing with a second token. I still hope nonetheless research and experimentation continues even if it happens outside of bitcoin.