Isostatic movement of the continents due to loading and unloading occurs over timescales of thousands of years.
Data from Topex and Jason have clearly shown a GMSL rise over the last 20 years (although not an acceleration) but local sea levels will be affected by both the eustatic thermal expansion due to changes in the oceans thermal vertical profile and geoidal-eustatic changes due to changes in ice masses.
There are many different things going on and we can't yet model them all.