I am not sure what point you're trying to make because of this message:
You see this page, because the system administrator of 000webhost.com is currently checking this website for malicious content. This redirect will be removed once we will finish manually checking all files on this account. As far we check over 100 websites, it can take about 2-4 hours to complete. If you are the owner of this website, you will get email confirmation once it's done. If you are a visitor - please come back later.
Based on what little information you've provided..
Themes will have to be remade for them to work correctly with 1.4. This is because 1.4 has many new features and the themes made for 1.2.x are not designed for them.
soo once 1.4 is out we need to make new themes?
Your MyBB 1.2 Themes (the CSS) will be automatically upgraded for MyBB 1.4. Your templates will be updated, but templates that you've changed will have to be updated via the differential tool provided in the ACP.
Is that currently implemented or not? (Can we do the upgrading now or do we have to wait..?)
You can start upgrading your themes now.