No... Adobe has announced in every venue/blog/forum it can reach that Lightroom is NOT going to be on the subscription service.
It has also been Adobe's (as well as most other software vendors) practice that when a new pending version has been announced, that the current version is eligible for either a free upgrade, and/or a heavily discounted upgrade price... If they didn't, then current sales would immediately stop while folks waited for the new version...
If you're on the cusp. and need to be assured of it, simply call Adobe and speak directly with a sales rep. and ask them what the upgrade option is...
I can't imagine why anyone would hesitate to upgrade from version 3 to version 4... professional or otherwise...