I'm not sure how this went into an Ikea discussion, but I'll help digress the conversation further. My group owned two land parcels that we eventually sold to Ikea in Milwaukee and Nashville, both markets of ~1.5 million. These are recent developments (within the last 3 yrs).
If Ikea's distribution platform has been built out to service the 1.5 million markets, it's not unreasonable for them to explore the next tier of tertiary metros between 500,000 - 1 million with regional pull that may support the demand and not stress the distribution channel. ie. Des Moines, Omaha, OKC/Tulsa, Madison, Grand Rapids, Little Rock, etc. Des Moines MSA is now over 600,000 with a semi-larger regional pull from another 100,000 - 250,000 in ancilllary non-MSA Central Iowa counties.
I don't know how likely it is for Ikea to plant a flag in Central Iowa, but they are in there 4/5th generation of development and that is when the national groups usually find their ways into secondary/tertiary markets.