On our journey to update our apps to run on 14.5+ we already faced some issues with the new editor.
This post is about another problem you may also run into.
If you used to define the toolbar in the CKEditor according to this doc you already noticed that it's wrong: the values for the toolbarType have to be capitalized, so full has to be Full and so on, an error we had for ages. By the way, it's Slim and not lite.
<xp:inputRichText
value="#{document1.rtf1}"
id="rtf11">
<xp:this.dojoAttributes>
<xp:dojoAttribute
name="toolbarType"
value="Slim">
</xp:dojoAttribute>
</xp:this.dojoAttributes>
</xp:inputRichText>
But running your apps on 14.5 will be disappointing since this property does not work anymore. The picture shows the result for all 3 toolbar types. 
Support pointed me to the "new" documentation here. Do you spot the difference? Me neither. This doc hasn't been updated, not even for the new editor.
I would wish not only for an update regarding the errors, but also for a reasonable implementation for the new TinyMCE. I would wish that I could use my old code and it will be translated internally when rendering the new editor so that I do not have to change anything.
Ok. this would be luxury, I know. We have to say goodbye to backwards compatibility, at least because of the JVM update. But I then expect a well thought-through documentation as you can not apply the official TinyMCE docs here. I guess this is just the tip of the iceberg as I have the feeling that XPages have just been ported to the new version(s) - an exception is of course the new editor.
We opened a case, and after several back and forth, I delivered a simple example app where you can spot the difference when running it on a 12.x.x and a 14.5 machine.