I believe the current answer to that is to make vague promises about how the vapourware known as the Lightning Network will solve all the problems.

well, you couldn't. Peter Todd is a btc dev and provided a lot of thinking on the tradeoffs. He stated in an interview (fairly confident in this) a 100x improvement in speed and is in favour of not increasing block size. Should check it out, the intetview was on a podcast on the LTB network on itunes.

So you will be able to. He has done a lot of thinking around tree chains and scaling and optimiztion.

Btc is limited inamount of coins and came first, its value is as a currency.

Eth is the first popular blockchaindb. Coins are needed to pay miners and powet dapps.

If a currency cant be traded it idnt worth anything, however sidechains seem to provide a way to convert from one to another