Nested Transactions in 7.5??

How realistic is it to expect nested transactions to make it into
PostgreSQL 7.5?

I can't think of anything I've heard of in the works for 7.5 that comes
close in importance -- with the possible exception of a native Windows
port. There are just *so many* cases where you want to be able to have a
stored procedure that spans multiple transactions -- having nested
transactions allows saving a whole architecture tier. Without them,
important aspects of business logic either have to be on the client (where
they don't belong) or you have to have a 3-tier architecture, which adds a
lot to the complexity of the system.