A question

I'm thinking of writing a bit of a time travel story -- guy goes on a
relativistic journey that goes wrong, comes back to Earth 1000 years later
to find things suck.  You know, that sort of thing.

My point is, I want to make a new English.  But I don't know what kind of
sound changes are currently occuring in our language.  Does anyone know?

My clumsy non-linguist ear hears a dropping of final /s/ and /z/, an
ellision (is that the right word?) of dentals after nasels, and a
conversion of unstressed /u/ into /a/.  So "I don't want you to go to the
park."  Might come out /ai don wan ja ta go ta da pak./

Still, this isn't weird enough for 1000 years.

What I want to know is, what general trends is english going through.  For
instance, are vowels getting higher, fronter, backer, etceteraer?  Is it
my imagination, or are /th/ and /dh/ going away (that would be a relief to
my Japanese students, I'm sure!)?