It definitely gave him an opportunity to demonstrate his acting skills and will open up some doors. I think one of the best things that could happen would be if he lands a role in a "mainstream" drama playing a character who is emotionally similar enough to Frodo to tap into that association but also distinct enough in terms of setting and plot to help avoid typecasting--sort of like Jack Nicholson could build on
One Flew Over the Cuckoo's Next by playing other roles with a similar type of character yet not so similar they limited his career, if that's a good analogy.
I'd also concur in hoping he doesn't try to counter his image by doing something conflicted. For some actors that might be a good way to broaden their acting options, but I don't think that would work for Elijah. He has a good image he should build on. Comedy would also be a good idea--if he cameoed in something that made a joking reference to LotR that would also help him build on Frodo's reputation while also establishing his autonomy.