Code Alien was intended to be UEP Systems' first installment back with the series since 2, and they heavily promoted it to North American audiences in 2001. However, a series of underwhelming game releases (which ended with the company going under) meant that Code Alien was never released outside of Japan.
UEP Systems' other series installment released before their dissolution, Cool Boarders Burrrn, was a Divorced Installment / Spiritual Successor by the time it hit U.S. shores as Rippin' Riders for the Sega Dreamcast. Not only was the game released soon after 3, but it has cameos from several characters that were in 2, along with various nods to the franchise (including the training course from 2). It is unknown how well the game would have fared if it had been promoted as an actual sequel to 2.
Cool Boarders: Sold Out, a cancelled PS2 title from 2002 that was intended to be developed by Idol Games after the release of 2001. It had a more cartoony style than the previous installments...and that's all we know about the project.