Every fifteen minutes each way round the Wimbledon loop? Presumably that'd cause some headaches with the single "loop" platform at Wimbledon? Or would the trams have to move?
If the Loop becomes a bit more self contained then you might well be able to justify squeezing 8tph alternating direction through Wimbledon, although the planners might feel violently ill doing it. In times of disruption the re-occupation of platform 9 is surprisingly quick. It's often quoted that a long term aspiration of TfL is to have a second tram platform at Wimbledon anyway, so at some point it's quite possible you could get platform 10 back, it really depends on where you could put new tram platforms - I've never yet seen any suggestions - and how much money you could throw together given that the Loop alone isn't going to justify much of a spend.
When the Wimbledon Loop comes up in threads like this, it's normally referenced that the signalling on the Haydons Road arm (?) is not really capable of supporting 4tph yet so improvements aren't imminent.
Hopefully everyone is resigned to the idea that the Inner SLL service is gone until at the earliest the delivery of KO2. The ELL replacement is likely to prove popular, so by then some kind of extra capacity may be required; certainly in the long term something might be desired. The ELL is very unlikely to have anything to give as it's serving several popular branches already. Realistically that means anything extra has to go to London Bridge. Goodness only knows what London Bridge will be handling/able to handle then, but maybe a London Bridge<>Battersea Park (or Clapham if they can find space) might look attractive.
I'll put all of that speculative nonsense up in the air along with new platforms at Brixton, increased frequency Victoria<>Lewisham, and my personal favourite Brockley High Level.