The usual canned answer would be "when it's ready and not before"
As a software engineer I truely appreciate the work Jon does and am in awe of his skills. If he does not do any releases for the next 5 years because of what ever "major update" he is working on im not going to lose any sleep over it. ST2 in it's current incantation is the single best editor I have ever used. Jon will release the next installment when he feels it is ready for general consumption. This could be next week or it could be 5 years from now.
I myself put aside a project because i burned out working on it. For the past few years I would try dive back in and almost instantly lose focus. ST2 has revived my "get up and go" and I am now working on it full time once again.
I am positive I will love what ever changes he is working on and even though I only just registered quite recently, if the next release is ST3 I for one will be upgrading (i hope it has virtual spaces tho