Yours was capped in accordance with the old adenhanced-corporate plan; we can upgrade you to the new one if you want, but the limits on databases, parked domains, addon domains, and subdomains are way lower than on your corporate plan. If memory serves, database limit is 2, addon domains 2, parked domains 2, subdomains 2, and email accounts 3.
In your particular case, yours wasn't one that was capped at 1gb either - your plan was considered a non-standard one and left with its original cap of 2500mb.
We can still put you on the current plan, but to be honest you're getting more out of the old one at the moment - I'd personally say keep the plan you're on until you need more than the 2500mb, and if that time comes jump to premium so you don't have to take a hit on the number of parked/addon/subdomains