Wiki says a 2000 capacity. From some coverage on tv the ground looks like it could get a number of scaffold stands erected to provide more. Depends on planning I suppose.
Good on them - take the RFU to court. About time someone did.
I've been there a couple of times within the last few years for games, and lived just round the corner for a while about 25-30 years ago when Ealing were just a fairly run of the mill local rugby club. Trailfinders' money has seen some development of the ground and investment on the playing side. There is a main stand/clubhouse/changing rooms etc on one side, and a scaffold stand with maybe 8-10 rows of seats at one end. The rest was just a collection of small portable stands on wheels plus obviously some standing on all sides. Definitely not up to Premiership requirements, so unless they already have an agreement in place with a local football team (Brentford would be nearest but they're spoken for) to allow them to come up then they're on a hiding to nothing anyway.
I think they'd be at serious risk of going the way of London Welsh. Surprise promotion that they weren't ready for. Hastily arranged ground share to allow them to come up. None of it properly thought through and bust within a couple of years. No-one wants that. I thought off the back of that fiasco and LW's legal challenge that all Championship teams who wished to be considered for promotion in the event of them winning the league had to demonstrate at the start of the season that they had something in place.