Seperating estate land sales from mainland land sales in the Search window is a good idea but I do not think it is currently being worked on.
This isn't just a "good idea", this is a major problem. People have found themselves stuck with money committed to island land they didn't really own, couldn't subdivide, couldn't resell. Really, island leases need to be in a separate tab from mainland sales, but being able to select "lease" versus "for sale" in the land types pulldown is the absolute minimum to prevent fraud.
Yes, I really mean that word. This should be given the same kind of priority as copybot, and things like the new "focus beta" can easily stand to wait another month or year.