It is not 100% fact at all. I also don't know why you keep saying they will update between now and October. It could easily be updated in November-December too, or January-February, as they have done in the past.
The thing that apple really needs to decide is what features they are planning on adding to the next refresh model, and whether it is worth it to put for instance, an IGZO display in this next (potentially minor speed-bump refresh) model if the larger Broadwell refresh is to occur a mere 6 months from that update.
I also find it hard to believe that Apple will do 3 refreshes within a 12 month period. My guess would be that if they are indeed forced to have Broadwell in Q3 2015, with Skylake coming in Q4 2015, that they will do the bare minimum for this refresh, have a redesign for the Broadwell model, and then a normal (feature added) refresh for Skylake in Q4.
----------
They are both U-series processors but they are not the same. The MBA's processor is a 15 W, while the 13" rMBP's is a 28 W processor.
Edit: You're right, the distinction hasn't garnered a delay between the two processors