It looks like TW is doing this periodically to generate revenue/interest for the upcoming edition.
https://store.thirdwire.com/project_sf2_complete.htm
If you already have all five games, they’re offering everything you don’t have for $50. If you add up all the DLCs for sale on their page, it isn’t a very bad deal. Of course, if you already have the majority of it, it might not be worth much.
The kicker is the free upgrade to the pending Windows 10 Edition. If a customer already has the Complete Edition, he or she gets anything TW releases in the future for free.
Not really sure it’s worth it, because it will largely depend on what support the studio gives the game. I really hope we see the current features refined to a more functional level than what they are. As fun as the series has been, so much of what the community has done involved working around the limitations of the game itself. If this is nothing more than an update for modern graphics cards, then it will be a disappointment to the fanbase. If the studio actually commits to working on the title’s shortcomings, then they have the potential to steal a lot of momentum from Eagle Dynamics’ Modern Air Combat that was promised two years ago and has yet to be delivered.