Before you actually start translating your master's thesis, you really should ask yourself whether the effort that you are going to expend on this is proportionate to your intended goal. If you intend to embark on such a time-consuming process, it should be based on more solid evidence than simply "I think an English version of the paper will help my applications for English-speaking schools". In particular, if this really is your main motivation, then it may be a good idea to post a separate question here asking to what extent such a translation can be expected to help your application.
Concerning your actual question, there is no reason why translating your thesis would need to involve updating it. A translation is just that: a rendering of an existing document which was written in one language in another language. You wouldn't go back and revise your thesis simply because it no longer reflects the state of the art, therefore there is no need to do so in a translation.
That said, while there is no need to do this, you can certainly choose to add some updates to your thesis. However, such material would need to be clearly marked, i.e. you would need to clearly distinguish between the original text and any later additions. One reasonable solution would be to add footnotes in some appropriate places. Such footnotes would then need to be clearly distinguished from footnotes which are part of the original thesis.