Paul, I'm not sure what gave you that impression. Maybe you are thinking of Oracle, where a "rownum" construction is used. (But not much I'm going to do is going to get us near running on Oracle.)
In practice, the only other DB we've even seen work to support is postgres, so it should be sufficient to show that it supports limit clauses. It does:
Pg supports OFFSET also. I suspect Koha will move to a broader DBI management interface before Oracle is fully supported. In other words, I wouldn't change any queries for it, and certainly not for 3.0.