In theory, no, it shouldn't take that long but the reality is some may never be fully converted. They all have massive overworlds with gs1 scripts tied into many things. We've asked them to convert but this usually comes at the expense of creating new content. When this happens we all know that players don't see improvements so immediately begin to complain that the staff are doing nothing.
The new will eventually replace the old which will in time no longer work. Not a perfect scenario but we're pretty much asking Ancient Rome to retrofit an entire city to modern day standards.