For the most part, simply do not be concerned about it. Really, for all the hype, the reality will barely be a blip in your travels.
For now, the roadblock is EES, which is an interconnected electronic entry system to be used and shared by all Schengen member countries. It is basically the e-gates you may be familiar with, but a database that will record your entries and exits. There have been some trial runs, you may have used the gates at exit, maybe even entry, but with a person handing out stamps after you go through.
After that system is up and working, then they will open up ETIAS. However, obtaining your EITAS approval will be much of a non-event, just go online, answer some questions, pay your small fee, and from a few minutes to a couple days, you get a notice of approval. So even if they announced it will be effective in a month, you will have plenty of time. Just look at the info on the UK ETA, the ETIAS will be almost identical in function.
Can you be rejected? Unlikely, but if you have had a felony that required lengthy incarceration in the last 10 years, then you are probably out of luck, but then if they were aware of your history now, they would deny you entry.
Now as for when, like I said, first, really do not worry about it, but the task of getting 29 individual countries, some EU, some not, to independently fund and implement a data system at all of their entry points (land, air, and sea) and then get those points to work together, is not a small task. Projects like this are more akin to herding cats than an effort led by a strong central authority (there really is none in this case). The betting man would probably say the possibility of implementing ETIAS this year has already passed. You may see more "e-Gates" at airports, they will continue to work on the system, but it really does not seem to be going well.