If you're only looking to play games at 1080p or 1440p resolution, then a 3060 Ti would be more than enough to handle your needs. The current 30 series GPUs are powerful enough to handle most modern games at 1080p or 1440p with high graphics settings, and should provide a great gaming experience.
As for whether you should wait for the 40 series GPUs, that ultimately depends on your budget and how urgently you need a new GPU. The 40 series GPUs are expected to be more powerful than their 30 series counterparts, but they may come at a higher price point. Additionally, it's still unclear when the 40 series GPUs will be released, so you may be waiting for several months before they become available.
If you need a new GPU now and have the budget for a 3060 Ti, then it may be worth making the purchase. However, if you're willing to wait and want the most powerful GPU possible, then it may be worth holding out for the 40 series releases.