Tasks, Notes, and Notes field for an Address Book contact have a character limit of approximately 4048-4095 characters. Is there a way to increase or remove these limits?

Doubt it...

Sorry, looks like there is no way to change it:

Data limitations for wireless calendar synchronization

Thanks. This is an annoying limitation for what is otherwise a great device.

As far as task and calendars go, I think it's a fair limit. I don't plan on using a calendar note or task not to keep tons of data, esp if the calendar item is a recurring one. The memos on the other hand, I agree with you. However, I've been using ideaMatrix and I think it's able to keep a note of 32k size, which is handier for note-taking than the built-in memo app.

Cheers!
-h