Any other wallet that works with the wallet file created with Electrum?
there is no reason for a file created by a wallet software to work with another software since they all work separately and always have ways to let you export your keys. for example when Multibit stopped they released a simple guide for users to import their keys in any other wallet such as Electrum. and the keys are important not the file itself.
Can I trust that electrum wallet will always work?
Electrum is open source so we already know what is happening under the hood. if some day it stopped being updated you still can export your keys from it to import in another wallet and if it didn't work anymore you still can look at the source code (or ask someone who can to do it) and write a small and simple script to extract the keys from the wallet file you had.
in any case i would worry more about this instead:
I have placed the encrypted wallet file in the cloud,
that is generally a bad idea, although being encrypted makes it safer (depending on the strength of the password used) but it still isn't as safe as storing it locally or in cold storage.