To explain my negativity, despite dropping out of the pool quite late in 2018;
I think BA will get some new aircraft next year. They might not take all the 787s they have scheduled for delivery early next year, but will take some - maybe 5 out of the 7 they've got scheduled between now and summer '18. Any SH (A320/321neo) aircraft will be more or less pro rata replacements for retiring aircraft, or sent to Spain, or elsewhere.
So there will be a need for new pilots in the spring, but I think the bulk of it will be met by the FPP cadets, the general overcrewing that BA seems to have at the moment, and lastly by people in the hold pool who are above me - but even then not many, maybe a dozen. If I had an expiry date between Dec - Mar, I think that'll be about the sweet spot and I fancy your chances. Before or after (I'm after) you'll be too far up or down the "seniority" to escape and drown in the pool.
Of course, all this rumour and speculation could be killed by an update from BA...