Toys R Us is leasing a large number of sites on a temporary basis: smaller stores and only for the Christmas season. Temporary leasing might be a trend to capitalize on, especially where you have vacant space in a decent geographic market.  And if you can combine it with a different, complimentary seasonal concept (ice cream or frozen yogurt? tax service?), it might eat up otherwise vacant space.
Costco is looking at former department stores for expansion locations. Costco would be a great addition to any center, even upscale ones. It has been shown that the consumer who likes Nordstrom also likes the bargains and experience at Costco. Many upscale centers have prohibitions on discount or club stores. While the prohibition may be outdated, it may nonetheless still apply.
Allowances are becoming increasing at risk. tenants are concerned about a Landlord’s ability to fund in these challenging economic times and are requiring significant dollars to be paid up front or early in the process. Conversely, Tenants who are having difficulties at other locations are defaulting after receipt of allowance payments but prior to opening and so a Landlord is placed at great risk if it pays any allowance prior to opening.  If  the tenant has off set right for any non-payment, tenant can probably protect itself from a defaulting landlord.  BUT, the tenant needs to preserve this right in any SNDA it executes.  For large allowance amounts, the time to recoup may be unacceptable. In these cases, an escrow at time of delivery and payment upon opening may be better.
Book stores have issues. Long considered an ideal anchor for a life style center, the E Reader and low pricing of big box retailers make the book store a difficult retail concept.
Outlet centers are really popular. Traditional centers should capitalize and try to include outlets in part. Again, landlords should revisit the prohibited uses in effect at the center.
Let us know what are other trends you are seeing ?