Not all new operators and routes appear on slot requests. Pegasus have just announced BHX-SAW starting December and I've never seen them listed on BHX slot requests.
So who knows for SOU? I think it could be a very interesting few weeks though as Nov/Dec is prime time for new route announcements for the following year.
Although I personally think the Jet2 brand/product are a good fit for SOU, they announced their new LPL S24 base months ago so I'd be surprised if they now announce S24 routes from SOU at this (for them) late stage. In addition, they only seem to launch 4 aircraft based as a minimum (can SOU accommodate 4 738 at the same time?) and summer season sees them operating virtually 24 hours a day at most bases with some arrivals through the night followed by a wave of early departures. I thought there were night flight restrictions at SOU?
Very happy to be proved wrong though!