I might add on to that. Keep it ready, and if it does get pushed to the cloud, keep the half-rack as a "disastrous recovery" [sic] site.
At the minimum, one can buy a small tape library (a single drive HP one that is 2-3U can store 300 TB, all encrypted, using LTO-6 tapes.) Add to this a 1U machine via a SAS card, and you now have archiving capability. A HP or Dell drive array is also 2-3Us, so add that onto the machine via your protocol of choice (SAS RAID 6), and now you have a place to stash critical data for long term backups. That way, if the cloud storage provider dies, you still have access to database dumps, old purchase orders , payroll records, and other critical info.
Even with the assurances of "we have 'passwords' and 'firewalls'" that cloud providers give, it is wise to have core company data in two physical (or realistically one physical, one logical) locations. Mainly because of the "all eggs in one basket" item. It is only a matter of time before some criminal organization hits a large cloud provider and dumps all the client data . No large business trusts one data center completely, so why should one trust a cloud provider (which is likely just one data center, but might be without any oversight how it gets run.)
Other uses of that half-rack of space can be to have a VM farm. The drive array is changed out for a SAN with two drive controllers, a switch is added, and 1U servers using 10gigE iSCSI are put in. If density is an issue, an HP Moonshot can be tossed in for 45 blades in a 4.3U chassis . That way, one may only have a half rack, but still be able to spin up plenty of VMs as scaled down critical hosts (be it AD DCs, Exchange replicas, database cluster nodes, and so on.)
Of course, this won't fit every situation, but if something happens to the cloud services, the half-rack can be used to keep the company limping along on the short term until things get restored.
Even after moving to the cloud, I'd keep that half-rack, if only as a place to archive data for the long term.
: The receipts and POs will come in handy if the BSA comes a knocking and decides to demand an audit.
: Could be for any reason. Any group who does cause a major, unrecoverable outage at a first name cloud provider will forever get their name on the map and in front page of the press, day after day.
: The remaining 0.7 of a U can be plugged by one's method of choice in a hot/cold aisle. Plenum grade pipe insulation (which basically is a brown pool noodle that has a fire rating) is one way. The Moonshot is mainly for VDI, but when one is needing to replicate an entire enterprise's configuration on a scaled down basis, this is also a good use for this type of architecture.