V8.0.0.18 is released for 3ds system firmware.
What have changed:
Main changes for version 8.0.0-18U
Update released: July 7th, 2014
Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience.
Can my R4i Gold 3dscard still works on 8.0.0-18U?

yes, just go with your R4i Gold 3DS. It is awesome, always can support the newest firmware.
Any other flashcarts could support 8.0.0-18U?
it is still testing...
more info: http://www.depot4u.com/original-r4i-gold-3ds-blister-pack-hot-wholesale-p-17053.html