The Old Firm will never, ever get into the EPL, and there are two absolute locks making that a certainty. First, it would require Chairmen of relegation-threatened clubs (and I'd put everyone from Everton and Aston Villa down in that boat, so more than half the league) to vote for their own demise. There will never be fewer than 6 or 7 objections at the very, very minimum. Second, such a move would cause absolute chaos for UEFA. You'd have Anderlecht looking to join the Dutch league, Copenhagen looking at the Bundesliga and Benfica eyeing Spain. It would be a disastrous precedent to set. Considering those two factors, I can't ever see it happening (thank GHod).
I actually feel sorry for all SPL fans. The Old Firm fans so desperately want their teams to matter (which no doubt is part of the reason for Rangers' financial problems) and yet all they have is each other, 4 times a year. That's it. Regular European involvement seems beyond either of them and the league is so weak that's unlikely to change. So they have each other in an annual death embrace, and nothing else. For clubs with big supports and great traditions (vile sectarianism aside) that must be so frustrating. And other SPL fans have to put up with 3rd place being the best they can ever do, and the odd bit of fun when they go to one of the Old Firm grounds. It's all just rather wind-swept, second-rate and sad.
