Yes, Elgin is being pursued - probably because the CAMPO TWG is so heavily tilted towards suburban interests, they had to throw them yet another chunk of meat (even though the commuter rail line to Cedar Park ought to have been more than enough, considering how badly it screws urban Austin).
As for "hopping on the streetcar" - keep in mind that a streetcar in a shared lane, which is what Capital Metro originally proposed, is actually slower and less reliable than a bus. If people won't ride the bus today, they won't ride such a streetcar. (Streetcar in its own lane is, of course, a completely different story).
Most of the "rail bias" stories you hear get this completely wrong - having compared GOOD rail service (with non-trivial segments of reserved guideway) with bad bus service. Seattle's Lake Union streetcar, on the other hand, is "bad rail";
as most recently seen here; and we'd be well-advised to avoid their idiotic example.
So far McCracken seems well-inclined to avoid the stupid shared-lane plan that Capital Metro started with. We'll see. His idea of adding the airport->downtown segment was to get a chunk where reserved guideway would be somewhat easy to do, and pull in a bunch more potential daily commuters (to both downtown and UT), since commuter rail passenger distribution isn't going to provide nearly enough people on this thing for it to be viewed as a success worth more expansion. (you get 2000 passengers/day max to distribute; streetcar needs 10,000 a day to be viewed as a success in my estimation).