In terms of further usability of an iPad 2, no. It is not worth it to replace the battery on an iPad 2. Apple's last iOS was iOS 9.x on an iPad 2. The forthcoming version is 11.3, or 11.5.
What this means is you will not be able to download and use many new apps coming out for iOS due to the restriction on iOS versions. Most new apps are restricted installing on to iOS 10 or newer.
Furthermore, iOS 9 has a lot of security holes that Apple won't fix (google KRACK vulnerability), especially ones that prevent the Safari browser from being hijacked.
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Cydia is a community that is slowly shutting down due to lack of interest. Also, a Jailbreak is actually a security exploit. This means you are allowing someone enter your iPad using a security hole to install software that is written by someone you don't know which does unknown things to your iPad and opens a door to more software that you don't know everything about.
@kwcze
In terms of further usability of an iPad 2, no. It is not worth it to replace the battery on an iPad 2. Apple's last iOS was iOS 9.x on an iPad 2. The forthcoming version is 11.3, or 11.5.
What this means is you will not be able to download and use many new apps coming out for iOS due to the restriction on iOS versions. Most new apps are restricted installing on to iOS 10 or newer.
Furthermore, iOS 9 has a lot of security holes that Apple won't fix (google KRACK vulnerability), especially ones that prevent the Safari browser from being hijacked.