The previously existing, classic version of Sites will continue to exist in parallel with the new Sites as we add capabilities that are similar to those found in the classic Sites. The classic Sites and the sites created with it will continue to follow the Sites-specific settings in the Google Admin console at Apps > G Suite > Sites.
Please note: In 2017, we’ll provide and recommend options to migrate your sites from the classic Sites to the new Sites. Beginning in 2018, we’ll send a timeline and instructions regarding the gradual process to shut down the classic Sites. The specific date for the shutdown of the classic Sites has yet to be set, but we’ll inform you at least one year in advance of that shutdown.
But it's no surprise, right ? Because they do this all the time; only I didn't expect they would do it this soon. This is just like what happened with many other Google products; they start a new service, offer it for free, seduce millions of global users into using it and then one day they discontinue it for no apparent reason or start a new one with a new shiny name and leave the predecessor with no further updates; old wine in a new bottle ! Haah!
What does this mean to me and many Google Sites users around the world ? It means that we have to migrate our sites to the "New Sites" and string along with whatever Google's doing OR take out the complete source code for the sites (if Google offers that) and host it on our own paid servers. I recently started paid unlimited hosting in bigrock.in for storing all the files I needed for my website. So hosting is not a problem, but porting or redesigning is. I'll have to create a similar site on my own (may be from scratch) and host it on my server. That'd be a tedious task considering that I have very little time for anything other than my studies these days.
Having said that, I've already tested the New Sites and it looks great. I still don't know how many features and freedom are there from the designing point of view and I don't know if I can design a website with a similar theme I have now. All I can say it's limited in terms of features, for now. Let's hope Google will add more features to Sites and let its users to easily migrate from classic Sites to new Sites. Meanwhile, I'll be trying to move everything to my own hosting server so that I wouldn't have to deal with any such problems in the future. The sooner you realize and do it, the better.
PS : Thanks to Google for providing this service and helping me to realize one of my dreams.