Its not every day the #4 offense gets to add a 23 year old 3 time all star, so let's look into Kyrie's expected return and how much of a boost the Cavs should see.
First I expect that Kyrie's mins will come at the expense of Jared Cunningham, Mo Williams and Matt Dellavedova. Kyrie has a career TS of 55.8% and had a 58.3 mark last season. I'll split the difference and assume about a 57% TS rate. Delly and Mo have been doing very well in this regard hitting at 55.6% and 56.8% respectively so not much of a boost at all under this assumption. Cunningham on the other hand has a TS of 47% on 3.3 attempts per game and 1.7 FTA per game appearing in 21/24 games. Kyrie should swallow all of Jared's meaningful mins and shots, so about 3.5 possessions a game will get a 10% TS boost. TS is set up so that a 10% boost is worth 0.2 pts, and the Cavs run at a pace of 93.1 possessions per game, so just replacing Cunningham shots with Kyrie shots is theoretically worth about 0.75 pts per 100 possessions. It doesn't sound like much but remember that JC is only playing 13 mpg and has a 16% USG.
Kyrie has also been a higher usage player than any of Mo, Delly and JC for his career, so he will also be taking shots from other team mates. The Cavs have the 5th highest TS in the league at 54.9% and of their major rotation players only JR Smith (47.7%) has a current TS below 54%. Taking an extra couple of shots away from team mates, unless they all came at the expense of Smith, is probably only worth a small amount. Lets call it 0.2 pts per 100 (+2% TS on 5 possessions a game).
Kryie is also better than Mo, JC and Delly at two other offensive facets. O rebounding and avoiding TO%. Kyrie has been one of the best scoring/passing guards in the league when it comes to avoiding TOs over the past few seasons, and the Cavs have been a little below average in this aspect so far this season. Irving's return could easily save the Cavs 0.5-1.0 possessions a game worth a .6-1.2 pts per 100 possessions. I'll settle in at 0.9. His better Oreb rate isn't worth that much, a full 1 percentage point higher than his replacements would be worth ~.2 possessions, and almost 0.25 pts per 100.
Simply dropping in Kyrie in place of his backups should give the Cavs a boost of around 2 pts per 100 possessions. This would take their Ortg from #4 in the league to #2 and with a .4 pt gap between them and the #2 team- this is without any positive impact on his team mates by drawing defensive attention or opening up better play options for his coach.