It is a lot of stuff to cover in just two episodes left.
However...
They've been building to this Royal Wedding all season. it's literally the only thing that's been mentioned in EVERY episode besides the fact that winter is coming.
So for the sake of good writing, show running, and pay off (which the GoT writers have been on top of so far) you HAVE to show the Royal Wedding. Otherwise it was foolish to make such a huge deal of it this year then let it sit in silence for a year just to be like "oh yeah that thing from last season" next year. the PW will lose a lot of momentum if the RW goes down and we don't get to see that in the finale. Particularly because everyone will see Joffrey's death coming and there won't be the big payoff of "holy **** everyone is dying" whenever they try to do these piddly little upper-class weddings.
Remember 10 weeks ago when everyone in here argued that there was NO WAY they'd show the Red Wedding this season?
I agree with this here.
They've been building up the Royal Wedding all season. I think that'll be the ep 10 and a great way to end the season. Especially with Stannis throwing the leeches into the fire this past episode (I missed that on my first read). Red Wedding, casually mention Balon Greyjoy dying between ep 9 and 10 (this doesn't need much screen time), and then Joffrey's wedding. That would be an epic ending for this season.
Next season can introduce the Martell's because they're not really important until Tyrion's trial. There is still a lot that happens. Arya heading over the Narrow Seas, Euron coming back, Jon on the Wall, Bran and the Reeds, Dany and Mereen, Arianne's plot with Myrcella, etc.