@AndiBecker welcome to ERPNext!
Specifically - Py3 is on the way, no ETA but it should be ready by early 2018.
Roadmap - Roadmap is built collaboratively. We use GitHub Issues religiously and also map milestones.
I have also been tracking Odoo over the years and I think there are 2 major differences:
- In ERPNext, the primary focus is on the end-user and not the service provider.
- ERPNext will be built as a monolith (to stop fragmentation of the community with apps, improve end-user experience etc.) There will be apps, but they will not be first-class in this ecosystem.
Also we (I speak here as the founder/CEO of Frappé Technologies) intend to build ERPNext as a community not as a private company. We would like the ERPNext community to be made of small companies like ourselves and collaboratively. To formalise this, have the ERPNext Foundation (https://erpnext.org) - a registered not-for-profit with over 40 paying members now.
I undertand there are lots of Odoo developers who have years of experience in this industry and who believe in Open Source. I think there is a great opportunity to collaborate with this community on the principles of Free Software + Open Source. If you have specific concerns or queries, would love to take them here. (and anyone from the community is free to answer).
Edit: Most important, upgrades have always been free (and part of the core) in ERPNext since beginning.