I'm part of a team of 4 people in charge of the platform (1 release engineer, 1 dba, 1 IT guy, and me partially responsible for IT and also software configuration mgr) for a software company. 

We have experienced some sudden grow as we have hired one consulting company for providing us with a team of 5 sw developers working together with our people. In total we have reached a headcount of 50 (including administrative staff, general mgrs, project mgrs, analysts, developers and testers), even with this change, and given that we also hired another company providing us 5 another people in another outsourcing team for a different project, and as we also had to support them I don't see the need for it.

But my boss is insisting in hiring another release engineer, but we (as in 4 of us) also don't see the need for it. I was direct with him and confronted him about the idea but he still wants to have it his way.

These are scenarios that worry me: one is where the boss is hiding his intentions of get rid of one of us without telling directly. Other is when the workload is at its lowest after the outsourcing finishes or when inevitably the amount of headcount doesn't require a 5 people team for support. We also were planning to automate some stuff but when the other guy arrives it's likely to get to work on the new things, and then we get relegated.

How to handle above concerns?