Is there a solution in the meantime?
Lightroom does not have any features to share catalogs via the cloud with other users. While you can come up with workarounds using something like DropBox, there are many disadvantages and risks, and so this is not advised.
There are other software programs that do allow cloud sharing of photos libraries, such as iMatch. (Note: I am not endorsing or recommending iMatch as I have never used it)
If this is similar to your needs, you could add your vote here:
Adobe have the ability as they used it in their Adobe Revel cloud photo storage solution (now closed).
If it does ever come to Lightroom Mobile/Web I imagine it won't have all the features of Lr Desktop but then it depends on what your requirements are.
There is no current way to share a catalog, or sync collections between two different catalogs. You could sync collections to Lightroom Mobile and view and edit those images with a browser. You and your colleague could both access these images from different locations if you logged into the same Creative Cloud account that the master catalog is subscribed too. This is definitely not an ideal workflow though.