Even "old" systems by today's standards from 10-15 years ago are most likely 64-bit capable. On Windows systems, you can confirm this by pressing Windows + Pause/Break to bring up the System section from Control Panel, and make sure your "System type:" says both "64-bit Operating System, x64-based processor"
If you see that your system type reads "32-bit Operating System, x64-based processor", you will need to re-install a 64-bit version of Windows in order to continue playing Dota 2 after the switch happens. Back up your files first, fish out your Windows license, have an empty USB drive (or DVD) handy and grab re-installation media here for Windows 10, here for Windows 8.1, or here for Windows 7
On the other hand, if you see that your system type reads "32-bit Operating System, x86-based processor", you will need to retire your CPU (and motherboard/RAM) or laptop in favor of newer, 64-bit capable hardware to continue playing the game after the switch happens
macOS users (unless they're on anything before Mojave) and Linux users do not need to take action, as Dota 2 is only available as a 64-bit build on both platforms
Aghanim's Shard is now able to appear under Suggested Items (previously, the only way it appeared through the defaults was if it was explicitly specified as a Mid-Game or Late Game pickup on a hero's default build list or on a community list)
And lastly, in addition to that 32-bit deprecation notice being translated already, there are also some more localization file updates in a few different places, which are made possible through the continued assistance of dedicated Translators Like You – Thank You