What is the timeline?
if there is no cut-off date then it's just proof of concept for developers.
Alpha is exactly that - proof of concept (in a lot of ways)
They continue to work on 6.x, but 7 being a new kernel and everything means they have to make sure all existing functionality from 6.x is implemented and working properly with the major kernel changes (along with taking advantages of possible new efficient interfaces in the new kernels) so once they believe they've got a good working prototype, it'll move to Beta for public to help test.
Unfortunately, if we wanted to force their hand on v7 timeline/release schedule, they'd all but have to stop development on 6.x and that doesnt necessarily mean v7 will be quick, could you deal with 6 months+ of no further 6.x updates?
Software release cycles at the level of RouterOS are very time consuming things to get right. I'd rather have a good v7 then a rushed one.