Apparently, their source for this information shared details about Resident Evil 6 before it was announced — which ended up holding water. This same source shared details about Darkstalkers 4, including:
• The game will use a modified version of the Street Fighter X Tekken engine.
• The title has been in the works since last year.
• Principal development of SFxT was complete towards the end of 2011, which is when Ono is said to have shifted his focus to Darkstalkers 4.
This is still an unconfirmed rumor at this point, so you might want to temper your excitement, but this is potentially good news for Darkstalkers fans.