Without the heresy, the Emperor would have been able to implement the Imperial Webway properly and assuming Magnus didn't do another retard psychic message, revolutionized travel within the Imperium as they would have been able to significantly decrease reliance on Warp travel. With this and the Imperial truth still strong Chaos would have weakened over time, and the Imperium would have been able to consolidate their gains. Overall humanity would have had supreme dominance over their territory and likely sent out another crusade or expedition into different areas like into the Halo Zone as it is known in the 40th millenium due to having the Imperial Webway.
The only real threats could be from waking Necron tombworlds, or if this goes further into the future, the Tyranids.
My advice to you is to get married, if you have a good wife you'll be happy; if you get a bad one you'll become a philosopher.
In the grim darkness of the future the economy has even hit daemons, The Changeling is working at White Castle and Skarbrand is giving head in the alley next to Fateweaver's.You ever receive fellatio from a rhyming demon? It's a bad scene man.
Sticking your junk into a fang-filled mouth that breathes fire doesn't strike me as particularly smart.
Which is why that option should be available to any willing to take it.
In fact, there should be fang-faced, firebreathing demons on every streetcorner offering to pay 100 dollars to give BJ's. The gene pool would be vastly better off without anyone incapable of thinking it through.