I think it is too soon for Dorico to have an established version upgrade cycle. There was a grace period on the release of Dorico 2 and I suspect the same will be true of Dorico 3 - Steinberg have a policy of offering grace periods and I doubt this will change in the future. However, Daniel has made it clear recently that Dorico 3 is far from imminent, so waiting a few weeks before purchasing hoping that will put you into a grace period may well not work.
One possibility that I am sure was considered was releasing Dorico 3 before the new university year starts (in the UK, at least) in late September / beginning of October - but Daniel’s “not over the summer” comment (same post as Dan linked to) suggests they might have given up on this, unless they are thinking of that time of year as early autumn (fall)!
It makes more sense to my mind for the release of Dorico 3 to be driven primarily by features rather than date. If, as I expect, they are working on guitar notation for Dorico 3, that kind of big feature has to be complete, not rushed out to meet a date.
The upgrade from Dorico 1 to Dorico Pro 2 was about 20% of the original purchase price, which hopefully puts the likely cost into perspective. Dorico is not a cheap purchase, but hopefully several months of additional usage if you buy now helps justify the eventual upgrade cost. As Ben says, don’t forget the ability to crossgrade if you use a competing notation product.
There was recently a 30% off sale for Dorico as part of the Cubase 30th Anniversary sale. I’m not sure exactly who got the code - certainly you needed to be subscribed to the Steinberg Newsletter and I think you might have needed to be an existing Cubase 10 owner. Unfortunately the deal ended on 27 May. Steinberg Newsletter emails seem to be unreliable for many people, me included.