Do not put too much hope into Apple increasing it. It has to do with resolutions > individual pixel sizes. There is a reason Apple displays are drop dead crisp/clear/gorgeous: the resolutions are made up of tiny pixels. They cannot change the pixel size for one part of the screen only - it is impossible. It is either all or none.
Apple has always embraced minimalism.
Look at it this way: a screen resolution of, say 1600 x 1000 means there are 1600 pixels horizontally - if the resolution is 3000 pixels wide, then there are 3,000 of them in the very same space. Makes for a beautiful display, but individual letter (fonts) are made up of, say 12 pixels - on a 3,000 pixel screen, that makes the letters or images tiny.
This debate has been going on for years. Increase what you can: in Finder, you can adjust the minimum font size on the screen or in Finder windows. You can also adjust it within apps, but the menu bar is part of the OS installation and there isn't anything you can do unless you can find an adjustment withint the Accessibility options.