Hart will not be appearing because he has a meeting on Monday with a hand surgeon in Calgary, according to The Wrestling Observer Newsletter. The surgeon is flying in from Paris to meet with Bret and he was unable to postpone. Sue Aitchison from WWE called Bret to arrange his RAW 25 appearance but he didn't want to cancel the meeting with the surgeon and sent a text message directly to Vince McMahon to explain why.
Regarding Foley, we noted before that he was invited but didn't know if he would be able to make the show. PWInsider adds that Foley already had a family vacation booked that would conflict with the RAW appearance. Foley reportedly feels that it makes no sense storyline-wise for him to show up for a special celebration show just months after being fired by Triple H and RAW Commissioner Stephanie McMahon from his job as General Manager. Foley feels that they need to sell the angle for at least one year before he's brought back.
In an update on Chris Jericho, Dave Meltzer noted on Wrestling Observer Radio that there is still no deal signed for him to appear as of earlier this week. WWE did announce Jericho on Monday's RAW but as noted, that was done prematurely. Despite having no deal, Jericho is expected to appear. The two sides have been talking and apparently going over creative ideas.