Meg was at the bit three-way dance in Boston and, as far as we know from published works, no AI survived Crash 2.0.
Dodger survived, but we don't know what he's been doing since then, aside from that little blurb in System Failure.
Now, there's a lot of speculation as to what happened. Some think that they were fragmented and scattered around, thus creating the seeds for the new, much weaker, AIs.Some think that the AIs might have ascended, becoming a new level of digital life, with the one that goes around the most is that Deus became the World Tree that Technomancers follow. Still others think that some of the AIs survived, but reformated themselves to blend into the new Matrix. Every other day, "Blank is really Deus!" gets floated in the conspiracy threads on the ShadowSea and, less often, JackPoint. You don't hear such things about Meg or Mirage.
No one ever really mentions the Fourth AI of olden days.
Lots of mystery on this front.
Personally, until something solid is said, there are two 'endings' for Dodger that work. One, Meg's gone, and he'll always remember her fondly, but is moving on in life. This is the sad ending that is more Shadowrun. The other version is that a tiny shard of her original form remains in his Cyberdeck, all of her power long gone as she's essentially just a sentient Agent program now, and that they sit and talk quietly on a regular basis. This is the Disney ending.
I know which one *I* prefer, but, your mileage my vary.