The closest analogy I can think of is that you are out on a limb, and sawing through the branch between you and the tree trunk.
The first point is that, if you insist on using a RAID0 configuration, you must regularly back up all data on it of any value. Unlike other RAID systems, RAID0 has no inherent redundancy and hence no protection against HD failure or corruption. Problems with just one of the disks will lose you all of your data if it is not backed up. The chance of this happening during the working life of a typical PC - say 4-5 years - is, I would guess, around 20-30%.
The question of whether the data will survive the system up-grade you are planning is difficult to answer without knowing the specifics of the old and new components. Even with the same motherboard and RAID controller, my view would be that success could not be guaranteed. With different components, I think that you should take the pessimistic but realistic view that the data will be lost.
The straightforward solution is to backup your data or your system to an external HD of the required capacity and to transfer it back when the up-grade has been successfully completed. I would recommend that this is done on a regular basis in any case.