The Manitoba Museum operates on revenue from entrance fees, government grants and public fundraising. It has recently been updating it's permanent exhibits which, along with their educational programming, preservation duties, etc., must take up a large chunk of it's budget, if not all of it.
I don't doubt the museum staff acknowledge the current science gallery is out of date and in need of a massive upgrade. My guess is they probably need a sugar daddy with extremely deep pockets to get the ball rolling with a huge headline-grabbing donation to start the fundraising for the proposed science gallery building. It's probably easier to build on something that's been started than to encourage people to donate to a project that's, for the time being, just a wish.
Here's a link to their annual reports/financial statements if anyone is accountancy-minded and is curious:
https://manitobamuseum.ca/about-us/annual-reports/