While VMware has planned to drop the guest operating systems patching capability from Update Manager (VUM), it seems to continue investing in the product. 
The company just released a very handy tool for VUM capacity planning called Sizing Estimator.

Sizing Estimator can forecast VUM 4.1 database size, patch store disk space, and temporary disk space by checking a number of parameters.
Its output includes:

• VUM database and server deployment model recommendations
• Initial disk space utilization in MB for database, patch store, and temporary space
• Monthly disk space utilization growth in MB for database and patch store
• The upper and lower bounds on the estimation, assuming a 20% variance

Definitively recommended.