It will take 3-5 years for Intel to build enough brand recognition and trust in the dGPU space to make a dent in AMD and Nvidia's combined market share.remember intel main reason to enter discrete GPU market is not about to win the graphic race. they do it to disrupt nvidia main source of revenue.
Depending on how well DG2/ARC does, it could be the i740 all over again with Intel scrapping the whole thing due to underwhelming sales and leaving customers stranded with garbage drivers. That is Intel's current dGPU legacy.