B.S. Have no relation (alas) to the CentOS team, except that I am proud CentOS user as well as probably you xD
Are plans in place for 6.1?
Most probably, it's not even considered now, taking 6.0 release pending into account. After 6.0 is ready (and it will take the great CentOS team a bit of time) they maybe will attend to the 6.1 challenge along with the updates for 5 series, 5.6 and 6.0.
IMO (and just IMO), it was bad idea to process both 5.6 and 6.0 at the same time. It got worse on the release time, and got terrible delay. Doing two independent things at once is really bad thing therefore.