Do ocean level rise estimates account for mantle elasticity and plate mass changes?
Sea level rise estimates use changes in relative mean sea level. The definition being:


  Relative sea level is the sea level related to the level of the continental crust. Relative sea level changes can thus be caused by absolute changes of the sea level and/or by absolute movements of the continental crust. 


In general, Mean Sea Level means the 'water level when it is still' (without waves). MSL is averaged over a determined period of time, such as a month or a year and it is measured relative to a fixed mark on the land (benchmark).

As MSL is measured relative to land, it can change due to changes in water volume or due to land movements. That is why we usually refer to it as 'relative sea level'. 

Long-term changes of sea level are called "secular" changes and include isostatic changes. The main reason for isostatic changes at a global scale is the Glacial Isostatic Adjustment (GIA).

The body of scientific work related to the contributions by different factors is extensive. For instance, I like Cazenave &amp; Nerem, 2004. Also, there is a lot of information about the relative contributions of each.

 Source: JPL-NASA

There is a lot more information about the regional distribution of sea level rise in: How will sea level rise be distributed across the globe?

Also, here is a good simple explanation of the factors affecting sea level.