Hello SMichel,
Please do not top-post (leave what you are replying to below your new message) in mailing lists.
What will I have to do to downgrade to the old Tor-version 'cause I'm willing to do so.
I would suggest against downgrading unless there is really no better option.
If you want to do something, what you can do is add the deb.torproject.org repository as a package source on your system. There is manual work involved in getting packages built and added to it due to it not being entirely handled by build bots, so delays may exist for holidays and such, but generally speaking, you can expect the latest stable release to be in there a few days after it has been tagged. Note that the repository is signed with A3C4F0F979CAA22CDBA8F512EE8CBC9E886DDD89 and a deb.torproject.org-keyring package is provided for installing the signing key so that rollout of a new key if/when it is required in the future is easier.
For example, to get the latest stable Tor release installed on Ubuntu Bionic Beaver (18.04 LTS) you could simply run:
cat << EOF > /etc/apt/sources.list.d/torproject.list deb http://deb.torproject.org/torproject.org bionic main deb-src http://deb.torproject.org/torproject.org bionic main EOF
apt-key adv --keyserver keyserver.ubuntu.com --recv A3C4F0F979CAA22CDBA8F512EE8CBC9E886DDD89
apt-get update
apt-get install tor deb.torproject.org-keyring
Official documentation on all of this can be found at https://www.torproject.org/docs/debian.html (along with an OS version picker) in case you are concerned.
And what's the problem with a version which is soon to expire if there (hopefully) be an update (in time).
If you are okay with running an LTS Tor version then there should really be no problem since Simon Deziel, the Ubuntu packager, has confirmed on Trac #25715 that Ubuntu Bionic (18.04 LTS) will ship with Tor 3.2 until a new Tor LTS is released which is when they start packaging that. (See: https://trac.torproject.org/projects/tor/ticket/25715#comment:4)
You can then expect it to look like how it looks for Ubuntu Xenial (16.04 LTS) now. You can imply Xenial shipped with Tor 2.7 until Tor 2.9 was released just by looking at the current state of the Ubuntu repository. As of writing, Ubuntu has Tor 2.7.6 in the base xenial distribution and Tor 2.9.14 in the xenial-updates and xenial-security distributions. (See: https://packages.ubuntu.com/xenial/tor)
I do not think it comes as a surprise that an LTS distribution would only have LTS versions, but still, it's worth keeping in mind then if you want the latest stable Tor version instead of the LTS version on Xenial right now you need to either build from source or use a different (most likely, deb.torproject.org) repository. Expect the same to apply on Bionic once the new Tor LTS is released and further stable versions start coming out.
The original thread/ticket was more of a public 'better safe than sorry' kind of concern situation about what the Ubuntu maintainers' plans are more than anything.
-- 4096R/A83CE748 Valters Jansons