Seems like the logical takeaway from this. Announcement from when "Rebuild of Evangelion" was still the tentative title:
REBUILD OF EVANGELION （仮）
Notice how the films break down here.
前編 (Part 1) - release Jul 2007
中編 (Part 2) - release Jan 2008
後編+完結編 (Part 3 + Part Final) - release August 2008
The "plus" notation indicates that the last two parts were to be packaged together; if they were two separate full-length films that just so happened to be released in the same month, they'd have separate listings. What's more likely -- that two full-length films are both being released in the same month AND back-to-back in a single showing, or that they were going to repeat the episodic nature of EoE and have one movie split in two parts? Just because you can't rule something out doesn't mean it needs to be entertained as a reasonable possibility.