[QGIS-Developer] QGIS 3.46 builds to use Qt6?

[Borys Jurgiel]

I like Marco's proposal of extending 3.40 for another couple of months 
and focusing on the next LTR, which be Qt6-only.

Personally, I prefer bumping up the version to 4.0 instead of breaking 
the API in the middle of the series. Windows users are already 
frustrated with broken plugins after recent Python upgrades from 3.7 to 
3.9 and then 3.12. Come on, it's been 7 years since releasing 3.0 (time 
flies!)

However, if we stick to 3.x series, 3.50 looks like "three and a half", 
which somewhat justifies this API half-break ;-) Such a compromise could 
look like this:

3.40 extended until Oct 2026

3.44 (Jun 2025) with official Qt6 builds (marked as more or less 
experimental, depending on major issues and the number of plugins ported)

3.46 (Oct 2025) with Qt6 builds as default

3.48 (Feb 2026) with dropped Qt5 support if there are no blocking issues

3.50 (Jun 2026) definitely is Qt6-only and becomes LTR in Oct 2026.

If anything goes wrong, we can postpone the new LTR to 3.52 (Feb 2027), 
but I wouldn't delay it by default to avoid extending the time of 
maintaining two APIs and (increasingly difficult) backports to 3.40.

Regards,

Borys