I wouldn’t bank on the 365s going anywhere just yet.
There may be a reduction in the overall GTR fleet size that may require a bit of a reshuffle, but I’d say the fact the 365s are about to be fitted with ETCS suggests you should be looking elsewhere.. I’m not privy to the conversations happening at a very high level, but if I had to guess, I’d go with the far older stock somewhere a little more Southern!
However, as said, I’m not privy to those conversations so could be completely wrong, but it would be very odd for the 365s to be scrapped whilst the far older 313s continue to linger on..