My manager just gave me a new responsibility, but I'm probably about to leave the job
Hi everyone! I've been at my current job for about 4 years as an assistant. The company is trying to grow a bit and wants to start working more on social media, outreach, and marketing to bring in more clients. My manager pulled me aside and said there's no budget for them to hire someone full-time for this role, so supposedly me and three other assistants are going to help with it. But then he made it pretty clear that I'll be handling most of the work. I don't have any real education or experience in marketing, advertising, or sales. His logic was basically that I'm "good with people on the phone," so apparently that means I can run marketing now lol.
The awkward part is that he has no idea that since April I've been in the hiring process for another job somewhere else. I'm just waiting for the background check to finish before they send me an official offer. It's with a large organization, so the checks are taking longer than I expected, but they'll probably get back to me within a few weeks or maybe at the beginning of the following month. Now I feel like the situation is weird because I've been given some random title I didn't ask for and don't even want, and maybe I should have said something before he started building his plans around me. At first he said it would only be temporary and that they'd hire someone for it after a few months, but now he's started saying it might be more like 5-6 months with me staying in that role. I honestly don't know what to do. Should I wait until I have the official offer in writing and then give notice, or tell my manager now that there's a chance I might be leaving soon?