Should "get new sensor data" be its own task in an RTOS?
The question you ask can not be answered in general. There are some common approaches, each with there pro's and con's.


Asynchronous read on demand. Fine when the process that needs the value can wait for the read to complete. Might be the best solution when reading is costly (for instance in terms of mAh).
Synchronous (periodic) read into a pool, users read from pool. Often a good compromise, especially when the users must process the value, even when it is not changed.
Synchronous (periodic) read, users are notified when needed (publish-subscribe, listener). This is often used for trigger inputs that happen only sporadically, like a key being pressed or released. Good idea when the cost of processing is relatively high.


In the last two approaches interrupts can be used instead of synchronous (periodic) reading.