Currently 46% of all Estate Regions are Openspaces - the rest are full blown 15000 prim regions.
I've just finished a 1000 region random sample survey of all the 22365 Private Estate sims. 17% of sims were closed to public access*- Of the 830 remaining in the sample 383 (46%) were openspaces, and 447 were full regions (54%) . The margin of error on these figures is +/- 3.3% at the 95% confidence interval.
When I just looked at those new regions (or new renames) since May when the pricing changed and the land store went fully online , 80% of these are openspaces (237 v 59) - There is a larger margin of error on these (+/-4.5%) . It becomes more marked when looking at those new in the past 30 days with openspaces accounting for 84% (+/-7.1%) .
In terms of Monthly tier (and assuming that all 2600 grandfathered private estates are still online) this represents about $4,067,000 per month for LL . With 4 full regions or 16 openspaces per server , LL need 3657 servers to host all main grid private estates.
At current region delivery rates and the same ratios in 28 days time 50% of private estates will be openspaces.
None of these figures include the 5046 Linden mainland regions.
During my survey I also got quite a good idea of the penetration of Psyke's Security Orb as well
- Luckly I could complete most region surveys in the 10 seconds before being booted
Edit:* There probably is some bias in the 170 which were not accessible to survey - Academic and corporate research sims were over-represented in this group - I'd hazard a guess there are a larger proportion of full regions in this group but that is just speculation.