So Howard Megdal (??) doesn't think Seattle would trade their #1 pick for Griner, Della Donne or Moore....
With Sue Bird nearing the end of her career and Lauren Jackson likely never returning, the franchise is getting a lot younger. Loyd and KML were the first pieces; Stewart will be the next piece (similar to Seattle drafting Jackson in 2001, then Bird in 2002).
Stewart, Loyd, and KML will all be on their rookie contracts. Because they all were/will be taken among the first four players in the WNBA Draft, they will earn approximately between $48,000 and $50,000 for their first year two years, approximately $55,000 in their third years, and approximately $62,000 in their fourth years. Moore is outside of her rookie salary scale and is earning the max (approximately $107,500 - $110,000). Delle Donne and Griner are in their respective final years of their rookie deals and will be commanding maximum salaries for 2017.
Basically, Seattle gets Stewart and Loyd for the price of one mid-career star. It makes sense to build up your young players as part of your core, then adding All Stars and near-all Stars around them at a lower cost, while maintaining salary cap flexibility.
Plus, with trades, you need a willing partner. Minnesota's core is older; Moore is the youngest in that group. Chicago traded Fowles last year, its previous big star; cannot see the team rebuilding by trading its second star in two years (and the reigning MVP and the focus of the team's entire marketing efforts). Phoenix also has an older core with Taurasi, Taylor, and Dupree; Griner is the youngest and the future.