I was just thinking of some examples of starlets who said they were "making a come back" but fizzled out/got cold feet/etc. before making their first comeback scene. One example that comes to mind is Kiki Daire. There was a press release about her reappearing on Porn Star Karaoke, and she was on the type 9 site for a while, but was soon removed from their site and hasn't been in any new release (from what I've seen at least)Lukeford.com linked to a blog post ,supposedly from her, which said she was pregnant(as good a reason as any IMO)
Another example is naomi. Ladirect even put out a press release lauding her return here But she was removed from the website in short order soon afterward, again without any new releases(again that I could find) .
A final quasi-example ,because she doesn't truly fit into this category, is Jasmine Tame. She's mentioned comeback for about 2 years & did indeed comeback for a couple weeks (in 2007?) but hasn't been in anything since then to the best of my knowledge (although she did shoot a scene in tampa recently).
All this isn't to say that there's anything inherently wrong with changing ones mind& there can be many good reasons for doing so, but it may be a lesson to not get too excited about a starlet's "return" until there's hard evidence in the "can" Any other examples that you may have would also be welcome.