Given your timeframe...
Given your timeframe, deep burial does make sense. Like you say, we may not be around in the future to take care of the waste.
A recent problem with salt:
Salt mine used for nuke waste unstable
Also we may be able to better deal with nuclear waste in the near future.
It would be alot harder to destroy the waste if it's buried.
Nuclear Fusion-Fission Hybrid Could Destroy Nuclear Waste
Here is a timeline of efforts to do something about the problem:
"The First 50 Years"