So I was thinking about this and the obvious answer is "no." They surely wouldn't mention KM or DS, so why MP? But then I considered the fact that at this point in their career, these Grammy nominations aren't coming so much because DT is making better albums than they were ten or twenty years ago. Much like Jethro Tull years ago with the Metallica fiasco, the nominations are a nod to DT's longevity and arguably their entire body of work.
That said, I think it's absolutely unnecessary to thank MP in an acceptance speech because the guys are always moving and looking forward not back. MP had no association with either of the last two albums, so why mention him at all? At the same time, it might be classy on their part to throw his name into the "thank you's" to acknowledge his considerable contribution to their career up to this point. Plus, it kind of sucks for MP that they started getting these nominations right after he quits. Tbh, I've been a little uncomfortable with how quick some of the other band members are to point out that the writing team has always been JR and JP, when MP was obviously a big part of it as well. You can't re-write that history and I think it would be a cool move on their part to tip their hat to him in that scenario.