Assuming I have Bitcoin in Circle and Coinbase (which are basically the big fiat replacement exchanges) and assuming they will adopt XT the second it is clear the move is going to be made (And they will because I have talked to both companies in depth and they fully support XT) - wouldn't it be safest and easiest to just leave my bitcoins in their respective Coinbase and Circle accounts?

And this is assuming a succesful XT fork where you assume XT "wins".  Is there any potential risk anyone see's in this scenario / strategy of just leaving your coins in the exchange wallets?