Vallejo still hasn't released a new Ral 7028 series of paint. They will not even comment or give any commitment as to whether or not they'll release a new set of these colors. Vallejo's current Ral 7028 versions (Air and Color) are Dunkelgelb Nach Muster not Ral 7028.
After much experimentation, I discovered a real good match to Ral 7028 using Vallejo's Model Air 71.245 Loam Beige. I lighten it with 10% Vallejo Model Air 71.075 Ivory for 1/48 military tanks and 20% for 1/72 tank subjects; 1/35, I'll shoot straight. Makes a great base (not too dark as other paint) for your weathering. I also lighten Vallejo Model Air Ral 6003 and 8017 with 71.075 Ivory (I don't like to use white because of its "washed out" appearance.).
I hope that you'll find this helpful...71.245 Loam Beige is a real nice Ral 7028 substitute on our German scale military models.