I been away for a while. Can I use official way of updating both system and games?
If you have Haxchi or CBHC installed, there's no reason not to update to 5.5.3. While a future update for the Wii U is highly unlikely, I would still block updates after updating to 5.5.3, just in case.
If you don't have Haxchi or CBHC, you can still update to 5.5.3, but you might have reliability issues with the web browser exploit.