yes, you can expand in the future but there are some caveats/best practices to expansion.  You always want to expand in the same increments as the original pool, so if you are using 6+2 and later one you want to add more NL-SAS drives ..best practice would say to use 8 drives again. If you were to expand another tier (say SAS), then you can have other options but from that point on you want to stick to the same increment size. You want to be on flare 32 so that data rebalance happens during pool expansion.