Well a generation is usually considered what... 25 years? 45 ABY might be later than the movies start, the Solos would be 35 years old at that point. Carrie and Mark average out at around 60 for filming the next movies, so simple math says 40 ABY... Which still gives us 30 year old Solo twins, and a 13 year old Ben Skywalker. That sounds reasonable to me... but then they could move the ages around too... we just don't know enough. 45 ABY only makes real sense for the fans that are hoping Lucas doesn't retcon major parts of the EU, which is something I don't see him caring about really.