The fork with the best development support is the most likely one to succeed long term.
This is also why ETC is inferior to ETH. ETH has the better dev team.
What makes you so sure that all the development teams that currently work on Ethereum-based
projects will continue working on them? Many of them were originally developing Bitcoin-based applications
and switched to Ethereum, because of several reasons (e.g. the stalling of BTC development due to issues
like the scaling debate).
I see a highly likely scenario that a promising new coin/network that is much more advanced than Ethereum
will be developed in 1-2 years that will attract a lot of the development talent that currently
works on Ethereum-based projects.
Most developers go to the coin/protocol that offers the biggest possibilities and the biggest hype (and probably
also the most money).