tl;dr - We're going to have another major wave; it will likely involve a lot of hospitalizations, not clear about death toll yet, but vaccinated people are very well protected.
Key points:
- Almost everywhere, the non-Delta variants are declining.
- Almost everywhere, Delta is increasing, rapidly.
- Rt estimates run about 1.3, that's enough for a pretty big wave.
- Mostly hitting the unvaccinated.
It seems clear to me at this time that we're going to see a major nationwide increase in case counts. If Delta is indeed about 2x more likely to hospitalize (compared to Alpha/UK variant) this could be a strain on our medical system again. Delta is also fairly good at infecting unvaccinated people who were previously infected by the original or Alpha strains. In that respect, it's vax rate that will drive the shape of the curves, not vax+infection-acquired immunity as before.
It's unclear how the relatively high vax rate among older people (most likely to die from COVID) will interact with this more-contagious strain. My seat of the pants guess is that we're probably in for another 100k or 200k deaths before Delta runs its course, but that fully vaccinated people are fairly safe.
Delta does seem to spread much better in children and young adults than previous strains, there are international reports of fairly large outbreaks in some schools. There are also reports of a couple of cases where delta was known to transmit between people who were near each other for just a few seconds. (Video footage of the contact, and sequencing of their identical viral genomes.) It's not clear if Alpha and the original strain did that or not, but we have so much more sequencing going on it's easier to spot now.