I undersatnd that in the near future the Creative Cloud applications will no longer support Type 1 Postscript fonts. What about True Type fonts or is the only acceptable format going to be Open Type?
AFAIK, support for True Type will continue. The Open Type specification is partially derivative of True Type, so despite being the "inferior" cousin-format, True Type support will probably survive for some time to come.
On behalf of Adobe, yes, support for TrueType fonts will continue for the indefinite future. As @John Mensinger explains, OpenType, both the CFF and the TTF flavours, are effectively extensions of the original TrueType format in terms of file format.
I'm using the Helvetica Neue LT Std font family in a few large documents. InDesign is popping up the alert that I am using "Type 1" fonts, but in the InDesign (v17.0, 2021) Find/Replace Font window, when I select this Helvetica Neue LT Std font, its Type details say it is "Open Type Type 1," and the info at the top right of window says "Type 1 Fonts: 0" See attached screenshot of this window below. Is this font family "Open Type" and to remain supported, or considered a "Type 1" that I'll need to replace? Thanks!
see into my reply to a question that is similar to yours:
Apple Unsupporting Fonts in 2023: Format Confusion
In my eyes it could be a highly misleading message.
Could be that the document you are using had "contact" with Type-1 fonts one time in its life. That information sticks to the document's code and was never removed.
( ACP )