Segregation at Wembley is done in quarters. So we will get 40,000+ initially. Carlisle are not expecting to sell many more than 15,000, so as long as they don't sell tickets in there 2nd quarter (as S****horpe did to prevent Luton from having extra tickets), we could end up with 60,000+ tickets. Which will be more than enough.
Even with the initial 40,000 it won't be difficult to get a ticket, the trickiest bit will be getting tickets together with ST's and MKD ticket holders being sold at different intervals.