There are a few theories floating around about the "effect" (red flash) at the end of the game. Some people say it's like other games, where a red throb indicates pain, as immediately after he turns around and takes what are presumably pain pills (which appear multiple times in the story). I personally think Watts or Rosalene (or perhaps both) will be the center of an upcoming game(s).
The red throb is very similar to the instances where Johnny's health is declining, indicating a declination of health of someone in the memory, perhaps Watts. If it is him taking pain pills, he has a sickness, and will probably die an untimely death, and will probably have regrets (like, not hooking up with Rosalene, or something bigger) that he will want solved.
There's also the scene with the 2 squirrels chasing each other (which happens twice), and some other scenes where Rosalene experiences deja vu. This deja vu could be a repetition in the memory of Rosalene, related to a particularly strong memory, if Rosalene is having her memories modified.
I agree. There is a part where Rosalene says she helped Neil cheat to get the job and he is definitely suffering from some kind of painful wasting disease. Rosalene tells him to go watch Johnny and he says "watching someone wasting away isn't my thing." He also says he rather OD than be reliant on pills.
My guess is that the designers want to give us a series of games that are self-contained with the overall arch of Neil connecting with Rosalene (perhaps unbeknownst to her). He seems very upset when River is deleted, despite having stated that he is not interested in romance. He may have realized that he was missing out mere moments before death. Hell, maybe it's just Rosalene's way of giving him a love story as a "going away present" before he dies.
I can't wait to see :P --- "So build that wall and build it strong, 'cause we'll be there before too long"