Indeed this is troublesome, unknown if the ISPs will want to provide their IP ranges to Microsoft and keep them up to date.
I can think of two mitigations, feedback is welcome
1) Allow IP ranges based on IP Class
Even if the IP changes, it usually changes based on a class (subnet). There is a limited set of IP ranges that ISP have, most of them have 1. You can tell what type of class they have based on your current IP.
You can go to http://whatismyip.com/ and check the IP class based on this table http://en.wikipedia.org/wiki/Classful_network
Example:
If your IP is:
45.17.0.102 it is a Class A and you can allow the range 45.0.0.0 to 45.255.255.255 the key number is the first number.
On the other hand if your IP is similar to:
137.24.1.23 it is a Class B and you can allow the range 137.24.0.0 to 137.24.255.255 because it is a Class B, they key number is the first two numbers.
As mentioned before, even large ISP have a limited set of IP ranges.
2) Disable the firewall
Obviously this defies the purpose of having a firewall, so only do it for a short period of time and fall back to option one when possible.
You can allow all the IP ranges if you put the range like "from: 0.0.0.0 to:255.255.255.255"
Also remeber to have strong passwords and update them frequently.
Thank you,
Alejandro Hernandez.