This heavily depends on the number of open and new bugs. As far as I know, there is currently no date, because we have seen where this leads to.
To accelerate the process: Test, test, test LS 4 and report bugs.
I personally would estimate a couple of months, but the LS developer team is usually more "optimistic" than I am.
Disclaimer: I am not deeper involved in this and my assumptions are based on what I pick up from time to time between the lines in the developer meetings every Tuesday.
I answer at the LimeSurvey forum in my spare time, I'm not a LimeSurvey GmbH employee.
No support via private message.
