Because Python 2.7 is completely mature and production ready and also allows you to write code which runs pretty easily on Python 3. Then you are marking Python 2.7 as deprecated version at the time where before you would have been just getting started.
Really this is down to whether you want to do something in Python now, or you want an excuse not to do it in Python for some time. It's not a bad excuse but it's also not a strong reason to wait.
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Because Python 2.7 is completely mature and production ready and also allows you to write code which runs pretty easily on Python 3. Then you are marking Python 2.7 as deprecated version at the time where before you would have been just getting started.
Really this is down to whether you want to do something in Python now, or you want an excuse not to do it in Python for some time. It's not a bad excuse but it's also not a strong reason to wait.